Document EP 2 143 397 discloses a pair of bite trays which are connected by connecting rods having a through-orifice comprising a first cross section that is larger than the cross section of the axis of the fixing device and a second cross section corresponding to the oriented radial fingers end section of the axis. In a first position, the orifice that passes through the connecting rod lug is aligned with the two radial fingers of the pivot and can be engaged. In a second position, the two radial fingers are no longer aligned with the profiled section of the through-orifice, preventing the connecting rod from being disengaged.
In this configuration, the axis of engagement and of disengagement of the connecting rod with respect to the pivot is unique and parallel to the axis of the pivot, which is transverse to the median sagittal plane of the device; this is a means of fitting which will therefore be referred to here as transverse. Blocking in the fitted position is achieved by contact between the radial fingers of the axis and the profiled section of the connecting rod end.
This system generally proves satisfactory when the fixing device offers a great deal of mechanical strength over a very small cross section, at the radial fingers of the axis. That requires the use of parts made of metal. This configuration also leads to wearing of the profiled section of the connecting rod lug, resulting in a loss of functionality.
Also known from documents DE202008011841U1 and FR2964853 is a device having a pair of bite trays and associated connecting rods having systems better suited to be produced in molded plastic. The pair of bite trays comprises lateral pivots intended to articulate the ends of the two connecting rods that connect a pivot of one bite tray to a pivot of the other bite tray and the pivot comprises means of elastically clip-fastening connecting rod ends.
As before, in this configuration the axis of engagement and of disengagement of the connecting rod with respect to the pivot is unique and parallel to the axis of the pivot. This is an elastic clip-fastening or clipping-together that is transverse.
This system generally proves satisfactory notably when the fixing device is fitted in such a way as to move the lower jaw forward by traction. The anterior fitting is therefore situated at the upper jaw and the lower jaw is moved forward by reducing the size of the connecting rods.
The traction configuration has a major disadvantage of keeping the user's mouth closed during the propulsion. That may lead to discomfort in certain individuals and limits the possibilities of moving the jaw forward, and therefore the effectiveness of the treatment.
In addition, during sleep, mouth-opening movements are numerous, particularly in the case of snoring and sleep apnea. When the opening force is greater than the retention of the bite trays on the teeth, that causes the bite trays to disengage and makes the treatment ineffective.
A propulsion system, on the other hand, offers the advantage of allowing the mouth to be opened. The anterior fixings are therefore positioned on the lower bite tray and the forward movement is performed by lengthening the connecting rods, as disclosed in document FR2964853.
In such a propulsion system, the connecting rods are subjected to compression under the effect of the return forces exerted by the lower jaw. In this configuration, the force transmitted by the connecting rod has a component the axis of which is separate from the axis of symmetry of the patient and the direction of which is oriented toward the outside of the jaw; this component directed toward the outside of the pivot may cause the connecting rod to disengage, particularly in subjects that suffer from bruxism.
It has therefore become apparent that it is desirable to improve the known device in order to obtain a system that is particularly well suited to being made in molded plastic for a forward movement by propulsion. That is the object of the invention.